The participants will get written feedback about their physical activity level after the baseline, and after 3, 6, 9 and 15 months of baseline compared to the current physical activity recommendations. Feedback will be created to illustrate participants´ activity level during the measurement week combining also the information from the diary. Feedback will be posted home and don´t include face to face interaction. As an incentive for participation, participants will also have opportunity to attend a body composition analyze and get short interpretation (15 min) of their own results in the research center.

The ACT group gets the same procedure as the REF group. In addition, they will participate the ACT based program. The intervention program consists of six group sessions, about 90 minutes per session during the 9 weeks period of time. All the participants get also pedometers for monitoring their physical activity during the intervention.

The program aims to enhance physically active lifestyle and well-being through important life values and build committed action based on the chosen important things. The importance is also placed to a mindful awareness and flexibility to everyday actions related to physical activity. The program don´t include psycho-educational elements or counseling of the health or the health benefits of physical activity.

The intervention program consists of six group sessions, about 90 minutes per session during the 9 weeks period of time. The group size is about 8-10 members per one group. All the participants get also pedometers for monitoring their physical activity during the intervention.

The program aims to enhance physically active lifestyle and well-being through important life values and build committed action based on the chosen important things. The importance is also placed to a mindful awareness and flexibility to everyday actions related to physical activity. The program don´t include psycho-educational elements or counseling of the health or the health benefits of physical activity.

Physical activity is measured objectively by accelerometer (Actigraph GT1M, GT3X, Actigraph, Pensacola, Florida) the last seven days.

Psychological wellbeing is measured using the Acceptance and Action Questionnaire (AAQ-2), which is a 10-item Likert-type questionnaire that assesses people's ability to take a non-elaborative, non-judgmental approach to their internal events, so that they can focus on the present moment and act in a way that is congruent with their values and goals, rather than with their internal events (e.g., fears, urges, prejudices).